Ring clamp fastenings are known, for example, from the Siemens Matsushita Components Datenbuch 1997, "Aluminum-Electrolyte Capacitors", pages 142 through 145.
Given these known ring clamp fastenings, the housing is fixed in the ring clamp with tension screws and nuts, and the ring clamp itself is then connected to a mounting plate with a screwed connection. Such a fastening of a capacitor to the housing jacket, however, is problematical because the wall thicknesses of the housing jackets are generally very low, and the material is composed of relatively soft aluminum.